Glazing, such as “insulated glazing units” (IGUs) and the like, are widely used in both domestic environments (e.g. double-glazed windows for homes) and in industrial settings.
Typically glazing is not well suited to environments where an inherent fire risk exists.
In general, glazing suffers from poor fire resistance due to the vulnerability of glass to thermal shock and the resultant loss of integrity. This can be a problem when considering the safety of users of the building in the event of a fire. Furthermore, in many countries safety regulations specify the fire resistance that needs to be exhibited by glazing used in a particular location.
Fire resistance is the ability of a barrier to control the passage of the products of fire from one side of the barrier to the other, to a defined level for a defined time under standard conditions of test. Three properties are commonly defined: Integrity (termed E)—The ability to control the passage of flames and hot gases, (thus preventing ignition on the unexposed face), Radiation (termed W)—The ability to control radiated heat emerging from the unexposed face and Insulation (termed I)—The ability to control conducted heat arriving at the unexposed face
This has led to classification systems for fire resistant glazing. For example, in much of Europe, regulations classify the fire resistance of glazing by the measurement of the minimum time for which the glazing maintains: (i) its structural integrity (termed E); (ii) its structural integrity and radiation reduction (within specified limits) (termed EW); and (iii) its structural integrity and insulation (within specified limits) (termed EI); when exposed to a fire. Standard tests to determine the classification of the fire resistance of glazing are defined and typically involve exposing the one side of the glazing unit to a fire and monitoring the integrity of the glazing, and/or temperature levels on the opposing side of the glazing, over time.
Fire resistant glazing in which the internal space between the transparent glass panes is filled with an interlayer of aqueous fire-resistant gel are described in U.S. Pat. No. 4,264,681 (SAINT GOBAIN), WO 03/061963 (FLAMRO), and WO 2009/071409 (FLAMRO). Fire resistant glazing comprising silicate based fire-resistant interlayers are also known (see, for example, WO2008/084083 (PILKINGTON)). These are commonly referred to either as glazing units or glazing laminates.
However, there remains a need for new and improved fire resistant glazing. In particular, there is a growing need for fire resistant glazing that meets the most stringent fire resistant criteria. Commonly, in Europe this means that the glazing maintains its integrity provides a barrier from radiation emitted (the radiation measured at 1 m from the sample is to remain below 15 kW/m2) and provides insulation from the fire (the temperature of the cold side of the glazing unit remains less than 140° C. on average and no individual spot exceeds a temperature of 180° C. above ambient) for a minimum of 10 minutes or more but usually for much longer. In addition, there are emerging market requirements for glazing that can maintain its integrity and radiation reduction for over 60 mins.
It is therefore an object of the present invention to provide glazing units that meet these stringent fire resistant criteria. Specifically, the object of the present invention is to provide glazing units which provide excellent insulation whilst also providing an excellent integrity and radiation barrier extending beyond the duration of insulation.